In just one day, the sun delivers about as much energy as has been consumed by all human beings over the past 35 years. So why haven’t we exploited more than a tiny fraction of this potential? There are many reasons: cost, storage, transmission, distribution, entrenched subsidies and technological challenges are but a few of them.

But the reasons not to take advantage of renewable energy are falling away. A report (PDF file) published this week by the Intergovernmental Panel on Climate Change (IPCC) found that close to 80% of the world’s energy demand could be met by tapping renewable sources by 2050, if backed by the right enabling public policies. I served as a Coordinating Lead Author for the Policy and Deployment chapter of the report, as well as member of the Summary for Policy Maker’s team, and I can attest to how much rigorous analysis and effort comparing data and sources went into this process and document.

The same Special Report on Renewable Energy Sources and Climate Change Mitigation found that the technical potential of renewable energy technologies “exceeds the current global energy demand by a considerable amount—globally and in respect of most regions of the world.”

These encouraging findings were released Monday, May 9, after being studied carefully, examined, and then approved by member countries of the IPCC in Abu Dhabi, United Arab Emirates.

The IPCC team’s 120 researchers found that the rising penetration of renewable energy technologies could lead to cumulative greenhouse gas savings equivalent to 220 to 560 Giga-tons of carbon dioxide (Gt C02eq) between 2010 and 2050. This could contribute towards the goal of holding the increase in global temperature below two degrees Celsius – an aim recognized in the United Nations climate convention’s Cancun Agreements.

Although the extent of renewable energy potential has been known for some time, the report’s optimism about the speed with which it could be tapped is promising. It puts the ball firmly in the court of the world’s policymakers, with its assertion that government policies “play a crucial role in the deployment of renewable energy technologies.”

We are already seeing this sort of clean energy scale-up moving from assessment to project design. On May 5 in Casablanca, World Bank President Robert Zoellick highlighted the opportunity and the potential of Morocco’s commitment to developing large-scale solar thermal power, as part of a regional push across North Africa backed by the Climate Investment Funds (CIF). The Bank Group, in partnership with the African Development Bank is supporting development of Morocco’s Ouarzazate Solar Plant, expected to be the first of its size in Africa. All of the specifics are not yet in place on this project.

With at least 1 Gigawatt in potential power, the equivalent of three times the world’s solar capacity today, Morocco and North Africa offer a tremendous platform to deliver solar power to Europe.

This week’s IPCC report complements previous studies by the same body, most notably its many “Assessment Reports”. Their findings remind us that just as human behavior causes climate change, changing that behavior is essential to stopping it.

Consensus among scientists that human activity is causing climate change has solidified with every passing year. In 1990, the first IPCC Assessment Report concluded that unequivocal detection of human impact on the climate was not likely for at least a decade. By 1995, the IPCC said that the “balance of evidence” showed “discernible human influence” on the climate. The 2001 report said that more than two-thirds of the warming of the previous 50 years was “very likely” due to human activity. This was raised to 90% in the 2007 report.

The 2007 Assessment Report also found that global warming will most strongly and quickly affect the world’s poor. This is an alarm bell. The policies needed to enable development and deployment of renewable energy must not only protect the poor from climate change, but also shield them from bearing costs of transition they cannot afford, and deliver them the energy services they need, but which are denied them at present.

To date the findings have been of increasing clarity on climate change, and in the Fourth Assessment Report, of the impact on the poor. Armed with this Special Report on Renewable Energy, my hope is to see the 5th AR add the finding, “Energy efficiency and renewable energy, if planned and deployed, can economically reduce our emissions of greenhouse gases to sustainable levels.”